Sometimes other notations for the couplings \(\rho \)  and \(\xi \)  are
used, e.g., \(\theta = \lambda /\rho \)  and \(\omega = - 3\lambda /\xi \) , or the ones used
in the special chapter [1]} about the
one-loop calculations and renormalization group flows in the
theory (REF ). The important part is the positive sign of the
coupling \(\lambda \) , as it is required by the positivity of the
energy of the massless tensor mode (graviton) in the high energy
region [2]}, [3]} (see also an alternative treatment
of the same problem in [4]}).
